Top United States health adviser and leading immunologist Dr Anthony Fauci is known worldwide as one of the most trusted authorities on Covid-19.
Fauci, who helped turn the tide in the fight against HIV/Aids in the 1990s, is director of America's National Institute of Allergy and Infectious Diseases and has advised six US Presidents on both sides of the political divide. He's about to add a seventh to the list - he will serve as President-elect Joe Biden's chief medical adviser.
As of today, Covid-19 infections in the US have surpassed 17 million in total, with a recorded 308,719 deaths - the highest figures of any country in the world.
More than 3600 people died in the US yesterday alone, and there are fears the worst is yet to come after Christmas gatherings and travel.
Fauci, who turns 80 this week, tells RNZ Nine to Noon's Kathryn Ryan the US will need to prioritise who gets the vaccine first.
"The supply is such that you don't have enough simultaneously for everyone at exactly the same time. We prioritise healthcare workers and then those in nursing homes because we've been particularly hard hit – a significant portion of the mortality, at least early on in the outbreak, was among the occupants of our nursing homes and care facilities.
"We would hope that if we can protect them, that would cover a significant part of the people that made up the mortality.
"However, once we get enough doses, we hope to be able to get such a large proportion of the population vaccinated that we can get, within a period of several months, what we call herd immunity. Then we have a blanket of protection over the country."
In New Zealand, the Government announced yesterday that it had reached deals to procure vaccines from two more companies, bringing the total to four, and what the Government believes will be enough courses to inoculate the entire country and Pacific countries.
Vaccination of the general population will not begin until the second half of next year and could run into 2022.
Fauci says he would hope New Zealand is a small enough country that we could attain the same thing within a short period of time.
"I think you're well positioned to really knock down this outbreak, in a very forceful way, by vaccination."
In the US, they're estimating that herd immunity can be achieved by vaccinating between 70 and 85 per cent of the population.
"We feel that if we can get that level of vaccination, we could get a blanket of immunity over the population that would essentially give the virus no place to go."
With the holiday season coming up, Fauci says experts are predicting a post-Thanksgiving and Christmas surge in cases and he's stressing to the American populace that they need to continue following strict public health measures such as wearing masks and not congregating in big groups.
"Nothing is going to change until we get such a proportion of the population vaccinated that you would have an impact on the dynamics of the outbreak, but we're not close to that yet."
Fauci says it is going to be up to richer nations to figure out how to support poorer and developing nations to get vaccinated if we want to see the end of Covid-19.
"This is a global pandemic and it requires a global response. Countries like the United States, New Zealand, the UK, and the European Union likely will have the resources to be able to be vaccinating the overwhelming proportion of their population.
"But we've got to make sure that in those areas of the world where they don't have the resources, that we can also get their population vaccinated.
"That's the reason why we've eradicated smallpox, why we have essentially eliminated polio in most of the world and we've done a major advance in having most of the developed world not have measles."
Vaccine confidence among the population will also be essential to widespread uptake and Fauci says that, from what he's seen, the makers of vaccine have been transparent and are having data peer-reviewed.
Another concern is that the Covid-19 virus will sufficiently mutate to get around a vaccine, but Fauci says that so far the data shows that it does not mutate to the extent of other viruses like influenza.
"What we've seen so far is that this is an RNA virus, so it does mutate, however the mutations do not seem to interfere with the part of the virus that is being blocked by the antibodies that this vaccine introduces."
Fauci has been a senior adviser to President Donald Trump. He had to contend with factually incorrect or misinformed statements from the President about the virus he was tasked with combating.
Different positions between the pair over the domestic response to the pandemic were frequent, and Trump - who contracted Covid-19 himself and hosted a Rose Garden event where several attendees subsequently tested positive for Covid-19 - often alternated between praising and dismissing Fauci's abilities.
Fauci says he will not comment on the particulars of working with the Trump Administration on fighting the virus, but says it is the worst respiratory virus the world has seen since the 1918 Spanish Flu.
"To have this degree of an explosion of outbreak in less than a year is really unprecedented.
"I would have to say, in all my experience, despite the fact that we've had serious deaths and morbidity with HIV, given the fact that this has taken place within the confines of less than a year, it is the most dramatic and impactful public health crisis that we've faced in more than a century."
With states in America having their own degree of independence from one another and the federal Government, Fauci says it has been highly challenging to have a consistent response to the virus.
"When you're dealing with a pandemic that does not know the borders between one state and another, then not having a uniform response is something that was a problem for us, and likely we could have done better if we had a more consistent response among the states."
Added to that, there has been a divisiveness in the United States compounded by conspiracy theories about the virus and distrust in institutions. Fauci says even wearing a mask or not has become somewhat of a political statement in America.
"It's really unfortunate because public health measures should not ever be politicised."